1. Field of the Invention
The present invention relates to feeding devices for wooden workpieces, and more particularly, relates to feeding devices for curved wooden workpieces.
2. Background of the Related Art
It is well known that shaping devices can be used to shape wooden workpieces into, for example, decorative wooden moldings. FIG. 1 illustrates a simple shaping device which has achieved almost universal acceptance in the woodworking industry and which is standard equipment found in most woodworking shops. Standard shaper 10 comprises a base unit, or base 11, and a vertically projecting cutting head 12. The shaper 10 further comprises a feeding device (not illustrated) for advancing the workpiece past the cutting head. The feeding device comprises a jig and preferably further comprises a means for automatically advancing the workpiece past the cutting head.
The jig guides the workpiece and maintains a specified spacial relationship between the cutting head 12 and the workpiece. The advancing means frequently comprise one or more motor driven rollers which automatically advance the workpiece through the jig. Until now, there has not been available a simple feeding device which can be used in conjunction with the shaper 10 and a wooden workpiece which is curved.
As illustrated in FIGS. 2A and 2B, a curved wooden workpiece 15 has lateral surfaces 16a, 16b, a top surface 17, and a bottom surface 18. The wooden surface further has a width W, a height H, and a curvature C. It is often desirable to be able to cut irregular outlines, such as an irregular outline 19, onto at least one of the lateral surfaces 16a, 16b of the workpiece 15. This may be desirable, for example, for the purpose of making arched doorways, circular windows, and other radial or elliptical shapes. Further, this ability is desirable now more than ever given the recent growth in the popularity of curved moldings.
It is known that devices can be made which are useful in the feeding of curved workpieces. Conventional feeding devices have suffered several disadvantages, however.
A first disadvantage of conventional feeding devices is that they can not be used in conjunction with standard shaper 10 and, as a result, the craftsperson is required to have two separate shaping devices. Conventional feeding devices for curved workpieces often require that the feeding device be purchased in conjunction with an entirely new shaping device which includes, along with the conventional feeding device, its own base and cutting head. For a craftsperson who already has a shaper 10, the cost of a new base unit and cutting head are duplicative and could be saved if the feeding device could be used in conjunction with the craftperson's standard shaper. Since there are a large number of craftspeople in the woodworking industry who already own a standard shaper 10, this is a problem that affects a significant percentage of feeding device users.
A second disadvantage of conventional feeding and shaping devices is that they often can be used only for curved pieces or only for straight pieces. As a result, the craftsperson is required to own and maintain two separate feeding devices. The fact that the craftsperson must use two separate feeding devices makes it even more likely that they will further own two separate shaping devices, as discussed above. In other words, they are likely to use a standard shaper 10 comprising a conventional feeding device for straight workpieces, and additionally use another shaper comprising a conventional feeding device for curved workpieces.
A third disadvantage of conventional feeding devices is that they are unduly complicated, given the purpose of cutting an irregular outline on a lateral surface of a curved piece of wood. They frequently comprise a control system (hydraulic, pneumatic or electrical), cutting heads mounted on cantilever arms, an excess of belts and pulleys, and other structures that introduce substantial complexity into the feeding device system. An unduly complicated feeding device is undesirable for several reasons. First, a complex feeding device is difficult and time-consuming to adjust for workpieces of different shapes and sizes, so that the downtime of the machine is substantial. Further, the increased complexity of the device increases the number of parts that comprise the device, and makes the device more expensive to manufacture. Finally, in a complicated device, even simple improvements become difficult to make. For example, it is often desirable in a feeding device comprising a plurality of rollers to motorize (i.e., make motor driven) at least one of the rollers so that the workpiece can be automatically advanced past the cutting head. However, when the feeding device comprises four or more rollers, a design decision must be made as to the number of rollers to motorize. If only one roller is motor driven, then the design challenge is to ensure that enough force is applied between the workpiece and the motor driven roller, so that a friction force can be imparted to advance the workpiece. If two rollers are motor driven, then the design challenge is to ensure that they are synchronized, so that the workpiece can advance smoothly past the cutting head. In short, complexity begets complexity, and a simpler feeding device is desirable.
A need therefore exists for a feeding device which can be used in conjunction with standard shaping devices, which can shape the lateral surfaces of both straight and curved wooden workpieces, and which is simple in construction.